The present invention relates to an ink jet system printer and, more particularly, to a printer head in an ink jet system printer of the ink on demand type.
Recently, an ink jet system printer of the ink on demand type has been developed, wherein ink droplets are emitted from a printer head at a desired time. In such an ink jet system printer of the ink on demand type, there is a problem that a nozzle orifice may become blocked and the ink droplets will not be emitted from the printer head, or undesirable air bubbles may be contained in an ink liquid filled in the printer head. The orifice blocking problem may be solved by providing an orifice cleaning system in the printer head. However, the air bubble problem has not yet been solved.
The above-mentioned air bubbles may be contained in the ink liquid filled in the printer head due to, for example, the incomplete sealing of the printer head. When such air bubbles are contained in the ink liquid filled in the printer head, the vibration energy supplied from a piezoelectric transducer attached to the pressure chamber is absorbed by the air bubbles. Thus, accurate droplet formation is precluded.
Accordingly, an object of the present invention is to provide a novel printer head system which ensures an accurate droplet formation in an ink jet system printer of the ink on demand type.
Another object of the present invention is to provide an air bubble detection system for detecting air bubbles contained in a printer head of an ink jet system printer of the ink on demand type.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, an air bubble detection system is provided for detecting the existance of air bubbles in an ink liquid disposed in a pressure chamber of the printer head. The air bubble detection system includes a drive source for activating a piezoelectric transducer attached to the pressure chamber for providing an initial oscillation in the ink liquid, and sensing circuit for detecting residual oscillation in the ink liquid disposed in the printer head. When the air bubbles are contained in the ink liquid, high frequency components are included in a signal obtained by the sensing circuit. In a preferred form, the piezoelectric transducer attached to the pressure chamber functions as an oscillator element when the initial oscillation is applied to the ink liquid, and functions as a sensor element when the application of the initial oscillation is terminated.